1. Field
The present invention relates generally to systems and methods of implanting a hip prosthesis and more particularly to a system and method of determining prosthesis orientation using indicia.
2. Related Art
Trialing during prosthesis implantation is generally essential in joint arthroplasty. Trialing steps ensure proper placement and function as well as assess range of motion and stability. In some cases, for example, in hip arthroplasty, an acetabular shell component needs to be implanted before trialing can begin. Likewise, other instances such as in knee arthroplasty, a tibial tray component needs to be implanted before trialing can begin.
In total hip arthroplasty, an acetabulum is normally prepared by reaming or other methods, and may require the use of cages or augments in cases of significant bone loss, degeneration, or deformity. An appropriately sized acetabular shell component is impacted, cemented, screwed, or otherwise affixed to a prepared acetabulum and a trial insert liner is attached. A femoral component which articulates with the trial insert liner is provided to the femur, and trial reduction begins. In some cases such as hip resurfacing, a trial liner may be eliminated.
Correct orientation of an acetabular shell component may differ between patients. However, it has generally been accepted that for a population majority, the longitudinal apex axis of a properly aligned acetabular shell component is generally inclined between about 40 and 50 degrees in abduction, normally about 45 degrees in abduction, and between about 20 and 30 degrees in anteversion, normally about 25 degrees in anteversion. Correct orientation of a femoral neck component may differ between patients. However, it has generally been accepted that for a population majority, a properly aligned femoral neck is generally inclined between about 35 and 45 degrees in abduction, normally about 41 degrees in abduction (i.e., 41 degrees above horizontal), and between about 10 and 20 degrees in anteversion, normally about 15 degrees in anteversion.
Due to the nature of hip arthroplasty, it is sometimes difficult to verify correct placement of an installed acetabular shell component intraoperatively. If an acetabular shell is misaligned prior to impacting, cementing, screwing, or otherwise affixing it to a prepared acetabulum, any subsequent trialing procedures and/or final implantation of the prosthesis may be compromised. Misalignment of an acetabular shell component may reduce articulation surface area, thereby adversely affecting postoperative performance, function, wear rate, range of motion, and joint stability.
Therefore, it is an object of some embodiments of the present invention to provide a simple and effective way to reduce the occurrence of misaligned acetabular components intraoperatively.
Conventionally, acetabular shell component alignment has been addressed intraoperatively using fluoroscopy and crude positioning instruments. These methods, while effective, require additional resources, personnel, additional instruments, and/or expensive machinery.
To this end, a surgeon may use fluoroscopic means to visually determine any gross misalignments during surgery. However, precise orientation angles of the acetabular shell component cannot be readily determined from fluoroscopic imaging. Alternatively, a surgeon may orient an impactor handle such that it is in longitudinal alignment with a corner of the operating room in order to achieve an approximate insertion angle of 45 degrees abduction and 25 degrees anteversion. Even more alternatively, some orthopaedic manufacturers provide alignment guides which may be used with impactor handles during acetabular shell component installation. Such alignment guides generally comprise what is referred in the art as an “X-bar,” “T-bar” or the like. A bar in the shape of an “X” protrudes from an impactor configured to install an acetabular shell component. The bar is attached to the impactor at predetermined orientation angle. With a patient lying in a predetermined position, the impactor is oriented such that the X-bar is parallel to the ceiling, floor, and/or table, and/or such that each extension of the “X” points to a corner of the square operating room. These methods, while effective, do not provide a finely calibrated visual feel-good device to a surgeon.
Indicia have been used on femoral heads to indicate a particular orthopaedic manufacturer, size, offset, or product SKU number. However, most indicia are generally found in the lip area or at the bottom of a tapered recess within the femoral heads and not located on an articulating surface.
Femoral head trial components of the prior art sometimes comprise a solid color indicative of a particular size or offset for a particular trial femoral head component. However, it is believed that such indicia are not configured to determine a spatial orientation of an acetabular shell component. Nor do such indicia comprise multiple colors on a single trial femoral head component.
U.S. Pat. No. 4,475,549 to Oh discloses an acetabular cup positioner of the prior art which utilizes a plurality of bar projections on an acetabular shell component impactor, the plurality of projections being configured for orientation purposes.
In U.S. Pat. No. 4,632,111 to Roche, a means for orientating an acetabular shell component comprises two threaded holes (66) and a threaded rod (64) with indicator ends (62). The rod (64), when placed in one of the holes (66), assists with positioning an acetabular shell component in a proper abduction angle. The rod (64), when placed in another of the holes (66), assists with positioning an acetabular shell component in a proper anteversion angle.
U.S. Pat. No. 4,305,394 to Bertuch, Jr., U.S. Des. Pat. No. D331,461 to Lester, and U.S. Pat. No. 5,364,403 to Petersen et al., further disclose prior art methods for positioning an acetabular shell component and associated apparatus.
In FIG. 49 of U.S. Published Patent Application US2007/0123908 published on May 31, 2007, and assigned Ser. No. 11/541,184, there is described an instrument which may include indicia or marks that can assist in the proper angular orientation of the modular components.
U.S. Published Patent Applications US2004/0122439 published on Jun. 24, 2004, and assigned Ser. No. 10/327,187 and US2004/0122440 published on Jun. 24, 2004, and assigned Ser. No. 10/327,527 describe placing indicia on first and second segments for determining the relative position of the first segment with respect to the second segment.
In U.S. Published Patent Application US2006/0058886 published on Mar. 16, 2006, and assigned Ser. No. 11/225,754, there is described an alignment trial system for a hip prosthesis comprising an interlocking trial femoral prosthesis and a trial acetabular cup prosthesis, wherein indicia is included to identify the engagement formation that is suitable for use in the right side and that which is suitable for use in the left side.
U.S. Published Patent Application US2004/0015238 published on Jan. 22, 2004, and assigned Ser. No. 10/346,316 describes providing a shroud for a femoral neck having indicia thereon for alignment purposes.
U.S. Pat. Nos. 5,002,581, 5,135,529, and 5,201,882 to Paxson et al. are drawn to a modular hip joint prosthesis comprising indicia adjacent to a connection portion, and a stem bearing one or more markings alignable with the indicia to indicate to a surgeon the relative rotational alignment between a trochanteral module and the stem.
U.S. Pat. No. 5,171,324 to Campana et al. discloses alignnement indicia on a protruding lip of a femoral component for rotational alignment purposes.
U.S. Pat. No. 4,004,581 to Heimke et al. discloses indicia means for measuring the depth of penetration for a hip bone preparation tool.
All of the above-referenced U.S. patents and published U.S. patent applications are incorporated by reference as though fully described herein.